Download Chapter 3: The Living Units

Chapter 3: The Living Units
Objectives:
1. Define cell.
2. List the three major regions of a generalized cell and indicate the
function of each.
3. Describe the chemical composition of the plasma membrane and relate
it to membrane functions.
4. Compare the structure and function of tight junctions, desmosomes, and
gap junctions.
5. Relate plasma membrane structure to active and passive transport
mechanisms. Differentiate between these transport processes relative to
energy source, substances transported, direction and mechanism.
6. Define membrane potential and explain how the resting membrane
potential is maintained.
7. Describe the role of the glycocalyx when cells interact with their
environment.
8. List several roles of membrane receptors and that of voltage-sensitive
membrane channel proteins.
9. Describe the composition of the cytosol; define inclusions and list
several types.
10. Discuss the structure and function of mitochondria.
11. Discuss the structure and function of ribosomes, the endoplasmic
reticulum, and the Golgi apparatus including function
interrelationships among these organelles.
12. Compare the functions of lysosomes and peroxisomes.
13. Name and describe the structure and function of cytoskeletal
elements.
14. Describe the roles of centrioles in mitosis and in formation of cilia
and flagella.
15. Outline the structure and function of the nuclear envelope,
nucleolus, and chromatin.
16. List the phases of the cell life cycle and describe the key events
of each phase.
17. Describe the process of DNA replication.
18. Define gene and genetic code and explain the function of genes.
19. Name the two phases of protein synthesis and describe the roles
of DNA, mRNA, tRNA, and rRNA in each phase. Contrast triplets,
codons, and anticodons.
20. Describe the importance of ubiquitin degradation of soluble
proteins.
21. Name and describe the composition of extracellular materials.
22. Discuss some theories of cell differentiation and aging.
Cell:
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I. Overview of the Cellular Basis of Life
A. Robert Hooke
1.
B. Schleiden and Schwann
1.
C. Virchow
1.
D. Cell Theory
1. A cell is the basic structural and functional unit of living
organisms. So when you define cell properties you are in fact
defining the properties of life.
2. The activity of an organism depends on both the individual and
the collective activities of its cells.
3. According to the principle of complementarity, the biochemical
activities of cells are dictated by the relative number of their
specific subcellular structures.
4. Continuity of life has a cellular basis.
E. Cell
1.
2. Generalized, Composite Cell
a.
b.
c.
II. The Plasma Membrane: Structure
A. Plasma Membrane
1. separates the body’s 2 major fluid compartments
a.
b.
B. The Fluid Mosaic Model
1. Fluid Mosaic Model
a. idea of plasma membrane as a think structure composed of a
bilayer of lipid (phospholipids) molecules
b. protein molecules dispursed in bilayer constantly change
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c. hydrophilic
1.
2. hydro =
3. philic =
d. hydrophobic
1.
2. phobic =
e. integral proteins
1. proteins firmly inserted into the lipid bilayer
2. transmembrane –
3. transporting things into & out of cell
4. channels –
5. carriers –
6. signal transduction –
f. peripheral proteins
1.
2. supporting filaments
3. enzymes
4. mechanical functions
III. Specializations of the Plasma Membrane
A. Microvilli
1. minute fingerlike extensions of the plasma membrane project
from free or exposed cell surface
2.
3.
B. Membrane Junctions
1. Tight Junctions
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a.
b. prevents molecules from passing through extracellular space
c.
2. Desmosomes
a.
b. spot welds between cells
c.
3. Gap Junctions
a.
b.
IV. The Plasma Membrane: Functions
A. Membrane Transport
1. Interstitial Fluid
a.
b.
2. Selectively (differentially) Permeable Membrane
a.
b.
c.
3. Two ways things enter/exit cell
a. Passive Processes
1.
a. Diffusion
1)
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2) molecules move from an area of higher
concentration to an area of lower concentration
3) molecules move along or down a
b. Simple Diffusion
1) unassisted diffusion of lipid-soluble or very small
particles
2) Osmosis
a)
3)
c. Facilitated Diffusion
1) type of diffusion of molecules that cannot pass
through the membrane because they are
dissolved in water
2)
3) carrier –
4) channel –
d. Osmosis
1)
2) occurs when water concentration differs on both
sides of cells
3) osmolarity –
4) if the membrane is impermeable to solute molecules
the volume of the solution will change
5) hydrostatic pressure – back pressure exerted by
water against membrane
6) water will diffuse until hydrostatic pressure is equal
to osmotic pressure
7) osmotic pressure – cell’s tendency to resist net
water entry
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8) tonicity –
a) isontonic –
1.
2.
3.
b) hypertonic –
1.
2.
c) hypotonic –
1.
2.
e. Flitration
1)
2) used pressure gradient – pushes solutecontaining fluid from a higher-pressure area to a
lower pressure area
3)
b. Active Processes
1.
2. usually used with substances too large to pass through on
their own
a. active transport – requires carrier proteins to go
against concentration gradient
b. vesicular transport – large particles and fluids are
transported across plasma and intracellular membranes
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1) exocytosis –
2) endocytosis –
3) transcytosis –
4) trafficking –
5) phagocytosis –
6) pinocytosis –
V. The Cytoplasm
A.
B. cellular material between the plasma membrane and nucleus
C. 3 parts
1. cytosol –
2. cytoplasmic organelles –
3. inclusions –
D. Cytoplasmic Organelles
1. 2 types
a. nonmembranous organelles – lack membranes
1)
2)
3)
b. membranous organelles – have membrane to maintain internal
environment different than surrounding cytosol
1)
2)
3)
4)
5)
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c. helps to keep biochemical activity organized
2. Mitochondria
a. threadlike or sausage-shaped membranous organelles
b. change shape constantly
c.
d.
e. enclosed in 2 membranes
1) outside membrane not special
2)
f.
g.
3. Ribosomes
a. small granules composed of protein and DNA
b.
c.
d. make 2 types of proteins
4. Endoplasmic Reticulum (ER)
a. extensive system of interconnected tubes and membranes
enclosing fluid filled cavities (cisternae)
b.
c. 2 varieties
1) Rough Endoplasmic Reticulum (RER)
a)
b) functions
1.
2.
3.
2) Smooth Endoplasmic Reticulum (Smooth ER)
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a) enzymes catalyse reactions
1. lipid metabolism, cholesterol synthesis
2.
3. absorption, synthesis and transport of fats
4.
5. breakdown of stored glycogen to form free glucose
5. Golgi Apparatus (Body)
a. stacked and flattened membranous sacs
b. modify, concentrate & package proteins & lipids made at RER
c. secretory vesicles –
6. Lysosomes
a. spherical membranous organelles containing digestive
enzymes
b. large & abundant in phagocytes
c. functions to
1) digest particles taken in by endocytosis (bacteria, viruses,
toxins
2)
3) perform metabolic functions (glycogen
breakdown/release)
4)
5)
7. Endomembrane system
a. system of organelles work together to
1)
2)
b. organelles
1)
2)
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3)
4)
5)
8. Peroxisomes
a. membranous sacs containing a variety of powerful enzymes
b. neutralize free radicals –
9. Cytoskeleton
a. cell skeleton
b. 3 types of rods
1)
a) element with largest diameter, hollow tubes
b) radiate from a small region called centrosome
c) determine overall shape of cell, distribution of
organelles
2)
a) strengthens cell surface
b) responsible for membrane changes of endocytosis and
exocytosis
3)
a) tough insoluble protein fibers
b) act as internal guy-wires to resist pulling motion on cell
4)
a) microtubules anchored near nucleus
b) containes paired centrioles – small barrel-shaped
organelles oriented at right angles forms mitotic
spindle
E. Cellular Extensions
1.
a. whiplike motile cellular extensions, occur in large numbers, on
exposed surfaces of certain types of cells
b. moves substances in one direction across cell surface
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2.
a. long singular cilia
b. propels cell itself
VI. The Nucleus
A.
B. Genetic Library
1.
2.
C. Most cells have one nucleus, some are multinucleate
1.
2.
3.
D. Once cell is anucleate
1.
E. 3 structures
1.
2.
3.
F. Nuclear Envelope (Membrane)
1. Double membrane barrier separated by fluid filled space
2. Outer membrane continuous with
RER
3. Nuclear Pore –
4. Selectively permeable
5. Contains nucleoplasm –
G. Nucleoli
1. Sites where ribosome subunits are assembled
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2. Usually 1 or 2 per nucleus
H. Chromatin
1. 30%
2. 60%
a. compact the DNA
b. gene regulation
3. 10%
4. Form chromosomes when cell is preparing to divide
VII. Cell Growth and Reproduction
A. The Cell Life Cycle
1. Series of changes a cell goes through from the time it is formed
until it reproduces
2. 2 Major Periods
a. Interphase
1)
2)
b. Cell Division
1)
3. Interphase
a. period from cell formation to cell division
b. metabolic phase
c. growth phase
4. Subphases
a.
1) cell is metabolically active
2) synthesizing proteins
3) rapid growth
b.
1) phase for cells that permanently cease dividing
c.
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1) DNA replicates
2) new Histone proteins formed
d.
1) final phase of interphase
2) enzymes, proteins (other organelles) are replicated
5. DNA Replication
a. DNA helix begins to unwind
b. Enzyme untwists double helix and separates DNA
c. Free nucleotides serve as a template for a new DNA strand
d. New DNA segments spliced together
6. Mitosis
a. 4 phases
1)
a) distinct pairs of chromosomes become apparent
(tightly coiled DNA and protein)
b) each pair of chromosomes is made of identical sister
chromatids, held together by a centromer
c) pairs of centrioles migrate to opposite ends of the cell,
form spindle fibers between them
d) nuclear envelope and nucleolus disappear
2)
a) chromosomes line up midway between centrioles
b) centromere holding each pair of chromosomes together
attaches to spindle fiber between centrioles
3)
a) centromere holding chromosome pair together
separates
b) individual chromosomes migrate in opposite directions
on the spindle fibers toward polar centrioles
c) cytokinesis begins
4)
a) chromosomes complete migration toward centrioles
b) nuclear envelopes develop around each set of
chromosomes
c) nucleoli develop
d) spindle fibers disappear
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e) cleavage furrow nearly complete
7. Cytokinesis
a.
B. Protein Synthesis
1. Gene
a.
b. nucleotide bases are “letters” of DNA
c. triplet –
d. tRNA –
e. rRNA –
f. mRNA –
2. Transcription
a. the transfer of information from a DNA gene’s base sequence
to the complementary base sequence of an mRNA molecule
b. codon –
3. Translation
a. language of nucleic acids is translated into the language of
proteins
b. anticodon –
DESCRIBE TRANSCRIPTION AND TRANSLATION:
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